Plasma-based systems include a supply source that is used to generate a signal. The plasma-based systems further include a chamber, which receives the signal to generate plasma. The plasma is used for a variety of operations including cleaning a wafer, depositing oxides and thin films on the wafer, and etching away a portion of the wafer or a portion of the oxides and the thin films.
Some properties of plasma, such as standing waves in plasma, etc., are difficult to control in order to be able to control uniformity of plasma etching or depositing. The difficulty in controlling plasma properties results in a non-uniformity in etching of material of the wafer or in deposition of material on the wafer. For example, the wafer is etched more at a first distance from its center than at a second distance away from the center. The second distance is further away from the center than the first distance. As another example, the wafer is etched less at the first distance than at the second distance. As yet another example, a higher amount of material is deposited on the wafer at the first distance compared to that deposited at the second distance. As another example, a higher amount of material is deposited on the wafer at the second distance compared to that deposited at the first distance. The non-uniformity in etching results in an M-shaped etch or a W-shaped etch of a wafer. The non-uniformity in etching or depositing results in a reduced wafer yield.
It is in this context that embodiments described in the present disclosure arise.